DNOs are licensed companies that own and operate the network of towers, transformers, cables and meters that carry electricity from the national transmission system and distribute it throughout Britain.
DNOs are responsible for allocating Meter Point Registration Numbers (MPRNs), which are the unique identifiers for individual supply points and correspond to respective regions. Their systems connect directly to the central database of electricity supply points.
As DNOs are naturally monopolies, they are regulated by Ofgem to protect consumers and ensure they do not abuse their position and overcharge for their services.
There are 14 licensed DNOs each covering a different geographically defined region of Britain and are owned by six different groups.
The DNO groups and DNOs are: